Industrial waste often contains toxic substances and waste gases such as dioxin that cannot be melted when the industrial waste is burned in an incinerator at a temperature below 1000° C. The toxic substances and waste gases are usually further heated in a melter to 1500° C. for melting the toxic substances and decomposing the toxic gas. Solid lumps of waste and harmless gas are discharged after hardening and cooling.
The wastes other than industrial products are also often treated in a melter where the wastes are melted, decomposed, combusted, and then cooled to form solid lumps.
However, these solid lumps thus formed are generally buried, for they could not be treated through further heating. Transport of the solid lumps from the melter to the burying site and the burying process are inconvenient and incur cost. Although the molten lumps have been used as graded materials, the utility is low. There is a waste in resources, as the fire-resistant properties of the solid lumps are not well used.